Iodine adsorption on InSb(001) at room temperature and low temperature: surface reaction

Abstract

Iodine adsorption on InSb(001)–c(8 × 2) at 273 < T/K < 325 is dissociative, forming an InSb(001)–(1 × 1)–I structure which is stable under electron bombardment and which has a work function 0.98 ± 0.03 eV greater than the clean surface. The adsorption behaviour is consistent with dissociative adsorption of iodine onto the indium-rich c(8 × 2) surface, causing breakage of the surface In—In bond in the dimer model for this clean surface reconstruction. For adsorption at 200 < T/K < 273 the (1 × 1)–I structure is formed first, followed by the formation of a multilayer surface iodide which shows no surface order and has a work function 1.23 ± 0.04 eV greater than the clean surface. From Auger electron and ultraviolet photoelectron spectroscopies the surface iodide appears to be enriched in In relative to Sb and consists mostly of InI, with an antimony iodide of unknown composition. The surface iodide, which is thermally desorbed at ca. 305 K leaving the (1 × 1)–I surface, undergoes electronstimulated desorption. The InSb(001)/multilayer iodide interface does not contain the (1 × 1)–I structure, this structure seems only to form during the initial/final stages of adsorption/desorption. Thin layers (10–20 layers) of the iodide cannot prevent contamination at atmospheric pressure and are therefore unsuitable as capping layers.